1. Field of the Invention
This invention relates to an optical-disk manufacturing device in which a side of a transparent plate, which is to be coated with a liquid resin, is pressed against a stamper, and irradiated by ultraviolet rays through the transparent plate so as to set the liquid resin, a pattern provided in the stamper, thus, being transferred to the cured resin separated from the stamper.
2. Description of the Prior Art
To manufacture an optical disk, such as a compact disk (CD) or a laser disk (LD, LVD), various kinds of methods have been disclosed so far, and a so-called photo polymerization method (hereinafter denoted by 2P method) is one of these methods.
According to the 2P method, the optical disk is made of ultraviolet-set resin. As shown in FIG. 1B, one side of a disklike transparent plate a FIG. 1A), such as a glass plate, is coated with the liquid resin b, and as shown in FIG. 1C, the coated side of the transparent plate a is brought into contact with a stamper c. Then, the plate a is pressed against the stamper c by a roller d (FIG. 1D), so far that the liquid resin is evenly distributed between the plate a and the stamper c.
As shown in FIG. 1E, the liquid resin b is irradiated by ultraviolet rays which are emitted by a lamp e through the transparent plate a so as to set the liquid resin, and as shown in FIG. 1F, the cured resin b is separated from the stamper c. Thus, the pattern provided on the stamper is transferred on a surface of the cured resin. Thereafter, the cured resin is metallized and coated with a protective film to obtain an optical disk f shown in FIG. 1G.
The 2P method has such features that the liquid resin is able to penetrate into pits of the pattern of the stamper even when the pattern is very minute, and further, a glass plate, which is better in optical characteristics than a plate of synthetic resin like polycarbonate, can be used as the transparent plate.
The transparent plate a must be transported from a position where a proceding process is performed, to another position where a following process is performed during the manufacture of the optical disk. For example, the transparent plate a is transported to a position where the ultraviolet-set resin is supplied on the side of the transparent plate, while, the plate a coated with the resin is taken out from the above position.
Exemplified in FIGS. 2 and 3 are the steps in the procedure in which the resin is supplied to the transparent plate, and a transport mechanism to transport the transparent plate before and after the step. A screen i having predetermined apertures h is stretched over a frame g, and under the frame g, a backboard k is arranged. Further, provided at the center of the backboard k is a disk setting portion l.
After the transparent plate a is mounted in the disk setting portion l, the frame g with the screen i is overlaid upon the backboard k, and the liquid resin b supplied from above to the screen i is spread over by a squeegee j, which is moved to press the screen i. Thus, when the screen i is raised, the liquid resin b is left in positions corresponding to the respective positions of the apertures h. The height of the left liquid resin b is substantially the same as the thickness of the screen i.
The transparent plate a is mounted in and taken out from the disk setting portion l of the backboard k by a transport mechanism m. An arm n of the transport mechanism m is rotatably supported at one end thereof, and movable upwards and downwards. Secured to the other end of the arm n is a suction head o, and from the suction head o, a plurality of suction tubes p, which have respective suction ports (not shown), project downwards. The suction head o is connected to a suction device (not shown).
When the arm n is rotated so far that the suction head o is brought to a position just over a disklike-plate supplying part of an optical-disk manufacturing device, the arm n is moved downwards to a position where the central part of a disklike plate a is attracted to the suction head o by suction. Then, the arm n is raised and rotated so far that the suction head o is brought to a position just over the disk setting portion l of the backboard k. The arm n is thereafter lowered so as to mount the disklike plate a in the disk setting portion l of the backboard k. After the suction is ceased to separate the suction head o from the disklike plate a, the arm n is raised and rotated so as to bring the suction head o to a predetermined position.
After the disklike plate a is coated with the ultraviolet-set resin b, the central part of the disklike plate a is again attracted to the suction head o so as to take out the disklike plate a from the disk setting portion l of the backboard k.
As may be seen from the above description, the suction head o sticks to the coated side of the disklike plate a, so that a stain caused by the suction head o is apt to remain on the coated side of the disklike plate a, and to be dissolved in the liquid resin b. This causes such troubles that errors are produced when recoding or reproducing of signals is performed, the metallized portion of the disklike plate easily corrodes, and the adhesive strength of the cured resin to the disklike plate decreases.
Moreover, the disklike plate a is apt to cause an undesirable displacement with respect to the stamper c when pressed against the stamper c during the manufacture of the optical disk. That is, as a stamping bed g, to which the stamper c is secured, is moved in a direction of arrow s see FIG. 4, the roller d abutting one end al of the disklike plate a is rolled in a direction of arrows t, so that the disklike plate a begins to be pressed against the stamper c under such a state that the other end a2 of the disklike plate a is spaced away from the stamper c. Thus, the disklike plate a is easily displaced in a direction of arrow u with respect to the stamper c due to friction between the disklike plate a and the roller d.
As a result, the disklike plate a sometimes rides on a projected core r of the stamper c, and is deformed or broken by the pressure of the roller d. The stamper c is also apt to be damaged. Sometimes, the disklike plate a does not completely come into contact with the stamper c due to shear between the disklike plate a and the stamper c, so that the liquid resin b does not completely penetrate into the pits of the stamper c, and further, locally has some foam. Thus, it becomes difficult to obtain a good transfer.
Such being the case, a shear detecting device, such as a photosensor, has been used to detect the shear between the disklike plate a and the stamper c. However, such device is not only expensive but also useless to preventing the disklike plate a from displacing with respect to the stamper c.